"It can be found in almost all the breads at Subway restaurants here in North America, but not in Europe, Australia or other parts of the world," Hari wrote. "Azodicarbonamide is the same chemical used to make yoga mats, shoe soles, and other rubbery objects. It’s not supposed to be food or even eaten for that matter. And it's definitely not 'fresh.'"

"Subway is using this ingredient as a bleaching agent and dough conditioner which allows them to produce bread faster and cheaper," Hari added.

Hari claims that the World Health Organization linked the chemical to respiratory issues, allergies and asthma, that studies linked it to tumor development and cancer, and is banned Europe and Australia.

She also created a video about the chemical, which she posted on YouTube and her blog.

"We are already in the process of removing Azodicarbonamide as part of our bread improvement efforts despite the fact that it is USDA and FDA approved ingredient," Subway said in a statement, according to USA Today. "The complete conversion to have this product out of the bread will be done soon."

The Associated Press reported that Hari has targeted other food companies before, including Kraft and Chick-fil-A for the chemicals in their products. Hari said she decided to focus on Subway, even though the chemical can be found in other foods, because of the company's healthy image it tries to project.

"I commend Subway for finally responding to me and now over 58,000 concerned citizens," Hari told USA Today about Subway's action and her petition. "Their swift action is a testament to what power petitions and individuals can have. I'd like to note that current Subway sandwiches still have this ingredient, and I urge everyone not to eat their sandwich bread until they have finally removed the chemical."